diff mbox series

[net-next,v6,4/4] net: vhost: add rx busy polling in tx path

Message ID 1532196242-2998-5-git-send-email-xiangxia.m.yue@gmail.com
State Deferred, archived
Delegated to: David Miller
Headers show
Series net: vhost: improve performance when enable busyloop | expand

Commit Message

Tonghao Zhang July 21, 2018, 6:04 p.m. UTC 
From: Tonghao Zhang <xiangxia.m.yue@gmail.com>

This patch improves the guest receive performance.
On the handle_tx side, we poll the sock receive queue at the
same time. handle_rx do that in the same way.

We set the poll-us=100us and use the netperf to test throughput
and mean latency. When running the tests, the vhost-net kthread
of that VM, is alway 100% CPU. The commands are shown as below.

Rx performance is greatly improved by this patch. There is not
notable performance change on tx with this series though. This
patch is useful for bi-directional traffic.

netperf -H IP -t TCP_STREAM -l 20 -- -O "THROUGHPUT, THROUGHPUT_UNITS, MEAN_LATENCY"

Topology:
[Host] ->linux bridge -> tap vhost-net ->[Guest]

TCP_STREAM:
* Without the patch:  19842.95 Mbps, 6.50 us mean latency
* With the patch:     37373.10 Mbps, 3.43 us mean latency

Signed-off-by: Tonghao Zhang <xiangxia.m.yue@gmail.com>
---
 drivers/vhost/net.c | 30 +++++++++++-------------------
 1 file changed, 11 insertions(+), 19 deletions(-)
diff mbox series

Patch

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index 2dc937e..a562828 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -501,29 +501,21 @@  static void vhost_net_busy_poll(struct vhost_net *net,
 }
 
 static int vhost_net_tx_get_vq_desc(struct vhost_net *net,
-				    struct vhost_virtqueue *vq,
+				    struct vhost_virtqueue *tvq,
 				    struct iovec iov[], unsigned int iov_size,
 				    unsigned int *out_num, unsigned int *in_num,
 				    bool *busyloop_intr)
 {
-	unsigned long uninitialized_var(endtime);
-	int r = vhost_get_vq_desc(vq, vq->iov, ARRAY_SIZE(vq->iov),
-				  out_num, in_num, NULL, NULL);
-
-	if (r == vq->num && vq->busyloop_timeout) {
-		preempt_disable();
-		endtime = busy_clock() + vq->busyloop_timeout;
-		while (vhost_can_busy_poll(endtime)) {
-			if (vhost_has_work(vq->dev)) {
-				*busyloop_intr = true;
-				break;
-			}
-			if (!vhost_vq_avail_empty(vq->dev, vq))
-				break;
-			cpu_relax();
-		}
-		preempt_enable();
-		r = vhost_get_vq_desc(vq, vq->iov, ARRAY_SIZE(vq->iov),
+	struct vhost_net_virtqueue *rnvq = &net->vqs[VHOST_NET_VQ_RX];
+	struct vhost_virtqueue *rvq = &rnvq->vq;
+
+	int r = vhost_get_vq_desc(tvq, tvq->iov, ARRAY_SIZE(tvq->iov),
+			          out_num, in_num, NULL, NULL);
+
+	if (r == tvq->num && tvq->busyloop_timeout) {
+		vhost_net_busy_poll(net, rvq, tvq, busyloop_intr, false);
+
+		r = vhost_get_vq_desc(tvq, tvq->iov, ARRAY_SIZE(tvq->iov),
 				      out_num, in_num, NULL, NULL);
 	}